Cameroonian soldiers drove militant Boko Haram insurgents back across the country’s northern border into Nigeria on Friday, a day after they killed at least eight people in an attack in the remote region that aid groups say is becoming a war zone.

Boko Haram fighters had stormed the village of Kerawa in Cameroon’s Far North Zone on Thursday, the local prefect said, the same day as a similar raid nearby and a suicide bombing in neighboring Chad. Lt. Col. Didier Badjeck, the army’s spokesman, said the military had caused heavy casualties in militant ranks, but no official death toll was available.